How to test voltage regulator output?

ILENGINE said:
there appears to be a 20 amp fuse in that wire. If that fuse(small chance) is blow or corroded(larger chance and possibly melted fuse holder) will cause the issues that you are having with the charging system.

This bypass wire is just replacing the purple wire in the diagram. If you get the temporary wire connected and it then charges then we know that the problem is in the purple wire. And you can go ahead and use your temporary wire as the direct replacement for the purple wire.
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Deafening applause for you! You are a Titan! It was in fact that 20 amp fuse -- blown to smithereens. Replaced it and my battery charges at 14v with everything wired back to factory settings.

When I ran that temporary wire that you suggested, the battery charged as it should. Then I knew to I had to find that 20 amp fuse you saw in the wiring diagram. It was well hidden or I would have checked it first. Your suggestions were stellar and you saved the day. Thank you a trillion times over!!!
 
ILENGINE said:
With the engine running full throttle connect the red lead to the B+ terminal of the regulator, and the black lead to the negative post of the battery. What is the voltage. Should read battery voltage. Now mow the red lead to the metal housing of the regulator while still keeping the black lead on the negative post what is the voltage. Any voltage over a about 1 volt indicated bad ground to the regulator and battery voltage would mean no regulator ground.

Just trying to make sure you are actually getting battery voltage to the regulator and not just creating a circuit that may not be there, and making sure the regulator is grounded.
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Score another win for yourself! I’d already tried two new regulators (1 Amazon, 1 OEM) and was getting -2v on the B+ to battery -.
This was first I saw about checking battery (neg) to regulator housing. Sure enough, it was showing 4v. Removed the bolt the regulator ground wire was under, cleaned them both up with some sandpaper and BOOM! Charging like a champ.
Thanks!
Jerry N
 
Everything has to be connected, and the voltage regulator body properly grounded. Measure output to the battery at the battery, not at the regulator output wire.

If it is not charging, then there is an open or corroded circuit between the regulator battery charge wire and the battery. An ignition switch or pin connection problem is fairly common.
 
What ILengine is saying in post 9 is :

It appears that the B+ post on the regulator terminal does not have a complete circuit to the B+ post on the battery.
When using the jumper wire you might consider installing a fuse of around 10-15 amps in the jumper wire.
Let us know what voltage measurements you get???????????
Sometimes this circuit is fused. Sometimes it goes through the ignition switch.
With a complete model number of your mower we might can find a wiring diagram?
 
Forest#2 said:
What ILengine is saying in post 9 is :

It appears that the B+ post on the regulator terminal does not have a complete circuit to the B+ post on the battery.
When using the jumper wire you might consider installing a fuse of around 10-15 amps in the jumper wire.
Let us know what voltage measurements you get???????????
Sometimes this circuit is fused. Sometimes it goes through the ignition switch.
With a complete model number of your mower we might can find a wiring diagram?
Click to expand...
The thread with the fuse issue was answered in 2019 and the wiring diagram for that issue was post 18. And the thread was brought back from the dead a few days ago with a repair of a regulator grounding issue from member @JNaughton using the testing that I posted in 2019.
 
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